Process for the delignifcation and bleaching of a lignocellulose material

Abstract

PCT No. PCT/FR93/00613 Sec. 371 Date Feb. 23, 1995 Sec. 102(e) Date Feb. 23, 1995 PCT Filed Jun. 21, 1993 PCT Pub. No. WO94/00234 PCT Pub. Date Jan. 6, 1994A method is provided for delignifying and bleaching a lignocellulose material, wherein an aqueous solution of a redox catalyst and an oxidant is reacted with the material. The catalyst comprises an organometallic cation of the general formula [(1)Mno2Mn(L)]n+, wherein Mn is manganese (III) or (IV) oxide, the two Mn's of this cation may form a pair in a III-III, III-IV or IV-IV oxidative state, n is 2, 3 or 4, O is oxygen, and L is a ligand comprising 4 nitrogen atoms co-ordinating the manganese.

We claim: 
     
       1. Process for the delignification and bleaching of a lignocellulose material in which an aqueous solution of a redox catalyst and of an oxidizing agent is reacted with the said material, wherein the said catalyst contains an organometallic cation of general formula (VII) ##STR11## in which: Mn represents manganese in a III or IV oxidation state, it being possible for the two Mn atoms of this cation to form the pair in the III-III or III-IV or IV-IV oxidation state, n has the value 2, 3 or 4,   O representing oxygen,   L represents a ligand of general formula (VIII): ##STR12## in which either R 1  represents the radical: ##STR13## R 2  then representing the radical: ##STR14## R 3 , R' 3  and R" 3  each representing, independently of one another, a group chosen from hydrogen, C 1  to C 4  lower alkyl, C 1  to C 4  lower alkoxy or halogen,   or R 1  represents the radical: ##STR15## R 2  and R' 2  then being identical and representing a group chosen from hydrogen or C 1  to C 4  lower alkyl,   R 3  representing a group chosen from hydrogen, C 1  to C 4  lower alkyl, C 1  to C 4  lower alkoxy or halogen.   
     
     
       2. Process according to claim 1, wherein the pH of the said aqueous solution is less than 7. 
     
     
       3. Process according to claim 2, wherein the said pH is between 2 and 5. 
     
     
       4. Process according to claim 1, wherein, after the oxidation reaction, the lignocellulose material obtained is treated with a basic aqueous solution. 
     
     
       5. Process according to claim 1, wherein the said oxidizing agent is added little by little to the solution of the redox catalyst so that there is not an excess of the said oxidizing agent which can react directly with the said lignocellulose material. 
     
     
       6. Process according to claim 1, wherein the said oxidizing agent is chosen from ozone, hydrogen peroxide, an alkyl hydroperoxide, hypochlorous acid, chlorine, chlorine dioxide or one of their mixtures. 
     
     
       7. Process according to claim 6, wherein the said oxidizing agent is hydrogen peroxide. 
     
     
       8. Process according to one of claims 1 to 7, wherein the said lignocellulose material is wood fragments. 
     
     
       9. Process according to claim 1, wherein the said lignocellulose material is paper pulp containing lignin. 
     
     
       10. Process according to claim 1, wherein the ratio by weight of the said catalyst to the lignocellulose material is between 0.1 and 10%. 
     
     
       11. Process according to one of claim 1, wherein the temperature of the said aqueous solution is between 80° and 100° C. 
     
     
       12. Process according to claim 1, wherein the catalyst/oxidizing agent molar ratio is between 0.1% and 4%. 
     
     
       13. Process according to claim 1, wherein the ratio by weight of the said lignocellulose material to the oxidizing agent is between 2 and 100.